Add default value to pool-prefix in Subnet-pool

If user tries to create a subnet pool without --pool-prefix,
it fails at the NeutronServer [1].
This patch tries to add a default value to the --pool-prefix
to try and resolve it.

Closes-Bug: #1564271
[1] : http://paste.openstack.org/show/492537/

Change-Id: I6cf324a5a8037048602e59c0bbfc93b40e73a74e

Author: reedip

openstackclient/network/v2/subnet_pool.py

@@ -111,6 +111,9 @@ def get_parser(self, prog_name):
     def take_action(self, parsed_args):
         client = self.app.client_manager.network
         attrs = _get_attrs(self.app.client_manager, parsed_args)
+        # NeutronServer expects prefixes to be a List
+        if "prefixes" not in attrs:
+            attrs['prefixes'] = []
         obj = client.create_subnet_pool(**attrs)
         columns = _get_columns(obj)
         data = utils.get_item_properties(obj, columns, formatters=_formatters)

openstackclient/tests/network/v2/test_subnet_pool.py

@@ -149,6 +149,7 @@ def test_create_prefixlen_options(self):
             'default_prefixlen': self._subnet_pool.default_prefixlen,
             'max_prefixlen': self._subnet_pool.max_prefixlen,
             'min_prefixlen': self._subnet_pool.min_prefixlen,
+            'prefixes': [],
             'name': self._subnet_pool.name,
         })
         self.assertEqual(self.columns, columns)